Managers of rooms, halls, and other shared places where people gather often wish to know the occupancy of these spaces (i.e. how many people are in the space). Occupancy is one metric used to evaluate the space, and whether there is a need to continue using it.
The oldest technique for measuring the occupancy of a space involves simply counting the people in that space at different periods. This technique is laborious, prone to error, difficult to repeat at odd hours of the day, and relatively costly.
In spaces equipped with work posts, such as call centers, the occupancy can be determined based on the presence, or lack thereof, of activity at each work post. In other words, if a computer at each work post is active, that is an indication that a person is present at that work post. This technique requires the presence of a computer connected to a network, and associated with a work post. This technique would therefore be ineffective with work posts or seats that do not have computers.
Another technique involves video surveillance of the space in question. This involves counting, manually or with the assistance of an electronic counter, all the people present within the camera's field of vision. It is generally difficult to include an entire space in the visual field of a camera. Furthermore, counters are relatively expensive and lack the precision and reliability required for certain applications.
Yet another technique involves a pressure sensor implanted in each seat. The pressure sensor detects a mass in each seat and thus is able to infer the presence of a person. Pressure sensors generally must be integrated into the seat during manufacturing. They are therefore difficult to use with existing seats, and with different types of seats. Furthermore, pressure sensors often generate false positives, cannot distinguish between people and inanimate objects, and wear down after repeated use.